If you want to step up the complexity of your extract brews, add some steeping grain to the recipe. And in an Oktobefest, I'd definitely go with some Munich and Vienna malts. I know these are base malts, but they add that extra flavor an Oktobefest needs. If you can get Munich extract, that's a good thing to go with also.
Other then that, use Hallertauer hops and possibly Saaz if you like them. I use all Hallertauer though, as I keep this type beer on tap at my house most months of the year.
Lagering properly does improve the flavor of this style, however, I've also had good results using the German lager yeasts at room temp to brew this style beer. In my opinion, it just turns out with a little more body.